Short circuiter



Aug. 3o, 1927.

E. P. LARsH Patented Aug. 30, 1927.-`

EVERETT I. LARSH, F DAYTON, OHIO.

SHORT CIRCUITER.

Application iiled February 15, 1924. Serial No. 693,019.

This invention relates to electric motors, and more particularly to ashort circuiting or operation changing device for automatically converting an alternating current motor from a repulsion, starting condition to an induction running condition, and vice versa, in accordance with variation of speed.

The `present construction embodies in a single structure, the advantageous features l of both the governor weight and garter spring type of short circuiting devices.

One of the purposes of the construction is to give deiinition to the movement of the short circuiting members, by which their movements into and out of contactwith the commutator bars will be decisive and which will eliminate the disadvantages of gradual engagement and disengagement.

To this end the construction embodies an annular series of centrifugally controlled contact members, located vadjacent to the lateral or terminal face of the commutator and concentric with the axis of rotation, which are capable of to and fro radial and l5 tilting movement under centrifugal influence. The construction is such that under centrifugal influence the `contact members will initially move outwardly in a radial direction'against the yielding resistance of a retaining member, which may be either of the garter spring type, or of the yielding cam vdisc type, the contacts engaging a llmiting stop as they approachthe limits of their outward radial movement, upon which they fulcrum for tilting movement CII into engagement with the commutator barsr under continued centrifugal influence.

Theobject of the invention is to simplify the structure as Well as the means and mode of operation of such circuit changing devices, whereby they will not only be cheap- .cned in construction, but will be more eiiicient in use, automatic in operation, uniform in action, automatically controlled and unlikely to get out of repair.

A further object of the invention is to provide such centrifugally controlled short circuiting means, which will Ipromptly respond to variations of speed, above and below a predetermined rate of rotation.

A further object of the invention is to provide a short circuiting or currentv changing break contact combined with suicient Wiping action to insure perfect electrical contact, and in which chatter or vibration and contact members, in lieu of the device, which will have a ,definitel make and mode ,of operation or ltheir equivalents asi hereinafter described and set forth in the claims.

In the accompanying drawings, wherein is shown the preferred, but obviously not necessarily the only forms of embodiment of the invention, Fig. l is a longitudinal sectional view of a motor commutator, to which the present form of short circuiting device has been applied. Fig. 2 is an end elevation of a commutator and short circuiting device, portions of which have been broken away. Fig. 3 is adetail sectional View similar to Fig. 1 but illustrating the employment of a spring pressed disc for retracting the garter spring illustrated in Fig. 1. Fig. 4 is a similar sectional view illustrating a modification.

Like parts are indicated by similar characters of reference throughout the several views.

The structure of the electric motor per se, forms no art of the present invention, whichpertains wholly to the short circuitingy means for the commutator bars, by which the motor is caused to operate alternately as a repulsion motor and an induction motor.

An alternating current, repulsion-induction motor of the single phase type to which the present invention is particularly vadapted is one, which asthe naine indicates, starts as .a repulsion motor and as the speed approaches its normal or maximum rate of rotation automatically changesl its character and runs as an induction motor. B'rieiiy described, is consists of a eld or stator of laminated toothed construction, having a single winding thereon connected tothe supply circuit and a vproc gfressivelyv wound armature or rotor with a commutator engaged by brushes during the starting or frepulsion period together with speed controlled devices for short circuiting the. armature Windings through the commutator after the armaturehas attained a predetermined speed, which speed controlled means in some instances lifts the brushes from the commutator simultaneously With the short circuitingv operation. There is no electric connection between the stator and the rot-or. The currents in the stator create an alternating flux, which reacts on the rotor and induces its rotation. This type of motor, therefore, starts as a simple repulsion motor Without compensating or auxiliary windings and operates as a repulsion motor until the rotor or armature approaches a synchronous speed or one commensurate with the windings, whereupon the speed controlled/devices operate to automatically short circuit the armature Winding through the commutator. Thus the motor is automatically transformed from a repulsion type into an induction motor having what is essentially a squirrel cage rotor. It is the improvement of the speed operated governing or short circuiting device which forms the subject matter of the present invention. One of the advantages of a machine ofthis type is that it is inherently a constant speed motor hav- .ing a high starting torque with low current consumption or minimum current surge.

The typical repulsion motor without compensation gives the most efficient starting torque possible while 4the single phase induction motorwith the squirrel cage armature or its equivalent affords the most effi-v cient motor when running.

A repulsion-induction type of motor combines these most desirable qualities in a single machine. As it possesses such high starting torque characteristics it is Well adapted for operating machinery which starts under full load, as pumps, air compressors, grinding mills, and analogous installations Requiring no starter, they are adapted for automat-ic control or distant operation. They start quickly `and operate quietly and smoothly.

The above is offered ,merely to facilitate a thorough understanding of the purpose of the invention, and with no intent nor desire that it shall in any way be construed as limiting or restricting the application or scope of .the invention.

Inasmuch as the construction of the motor per se forms yno part of this invention, it has not been illustrated. It is to be understood, however, vthat the short circuiting lmeans forming the subject matter hereof is applicable to various styles of motors of the character heretofore indicated. Referring to the drawings, l is the armature shaft, on which is `carried the usual commutator comprising the core 2 about the periphery of which are located a. continuous succession of commutator bars 3, insulated from the core'2, and from each other by intervening bodies of insulating material.

In the present instance, the commutator bars 3 are shown terminating flush with the core 2 and in a plane perpendicular to the axis of rotation. The core 2 of the coinmutator in the present construction is formed with a concentric recess 4. Located adjacent to the recessed face of the commutator is an annular series of independent contact members 5. These contact members are slightly sector or wedge shape, and are assembled side by side in an annular series. Each contact member is thus radially disposed in relation with the axis of rotation. and is laterally restrained or supported and guided through its radial movement by the adjacent contact members. The contact members are each substantially L-shape. They are arranged with the laterally projecting arm 6 of each contact members pro jecting within the concentric recess 4 of the commutator head. The lateral arms G of eachcontact member by its engagement with the bottom of the recess 4 limits the approach of the contact member 5 when in normal or retractedposition, toward the commutator. By its engagement With the peripheral wall of the recess 4, the arm 6 of each contact member, limits the radial movement of such member under centrifugal inluence. The contact members 5 are each formed witha contacting face 7, for engagement With the ends of the commutator bar when the contacts are in their operated po* sitions. The outer extremity of each contact is further provided With a notch or recess, Which registering with the corresponding notches or recesses in adjacent contact members form a peripheral groove in the annular series in which is seated a contractile circumferential retaining band 8, against the yielding resistance of which the contact members are radially movable under centrifugal influence. A guard plate or disc 9 is fixedly carried upon the shaft l, in spaced relation with the commutator. This lguard plate or disc 9 is preferably provided with driving vanes or small lugs 10 at spaced intervals which engage between successive contacts of the series, thereby dividing the contact members into groups and insuring the rotation of the annular series in unison with the commutator and shaft. The contact members 5 are so proportioned and shaped that the center -of `mass is either substantially in the plane of the circumferential contractile band 8, or due to the laterally extending arms, 6 and projecting contact face 7, such center may be slightly oliset from such plane inwardly toward the commutator head. The relation of the center of mass to the contractile retaining band is such that yupon rotation of the commutator and short circuifing members, the contact Y the contact member being members 5 will tend to move outwardly in radial direction and in substantially the vsame spaced relation with the face of the commutator, as when the contact members are at rest. As the contact members approach the outward limit of their radial movement, the laterally extending arms 6 thereof engage the inner circumferential face of the recess 4, which forms a limiting stop, arresting further radial movement of the contact member. The center of mass of offset laterally in relation with the point o engagement of the lateral arm 6, with the limiting stop afforded by the inner face of the recess 4, under further centrifugal'inuence the contact mem'- ber will tend to oscillate or fulcrum upon the point of contact, of its lateral arm 6 with the interior ofthe recess 4. Under such continued centrifugal influence, the contact member will be tilted about such fulcrum or bearing point, toward the commutator bar, and the face 7 will be brought into engagement therewith. Such operated position of the contact member is shown by dotted lines in Fig. 1. As the contact comes in engagement with the end ,of the commutator barthere willi be sometendency for the contact member to adjust itself by the arm 6 shiftingoutwardly upon the inner circumferential face of the recess while the contact face 7 has a limited sliding or wiping engagement with ythe end of the commutator bars. Thus there willbe a limited wiping or frictional contact, sufficient to keep the bearing surfaces always clean and bright. The engagement and disengagement of the contact members with the commutator bars will be decisive by the tilting movement into and out of engagement with the bar, while the members' are in their distended relation. Any tendency' of the contact members to creep under excessively high speed would be prevented by the engagement of the outer base angles of the contact members with the guard plate ordisc 9. Under normal cond1t1ons of operation'such excesslvecreep or necessity for limiting any shifting movelment of the contact members after their engagement with the commutator bars would be unnecessary. To facilitate the fulcrum movement of the contact member upon the limiting stop formed by the inner concentric face of the recess 4, the ends of the arms are somewhat enlarged and rounded tov afforda suitable rocking engagement; v

In Fig. 3 there is shown amodification,

where in'lieu of the circumferential 'garter spring. 8, there-is employed a beveled cam disc l1, mounted upon the shaft 1 for re#F7 ciprocationflin an axial direction against the tensionvof a spring 12. The construction is such that as the contact 'members move out- 'Wardly they engage the inclined interior surface of the yielding disc 11, and retract such disc against the tension of its spring 12, until the 'Contact members are arrested by the engagement of the lateral arms 6, with th-e concentric stop face of the recess 4.

Thereupon the contact members oscillate l ment with the commutator bars as before described. Upon relaxation of the centrifugal influence, the spring actuated disc 11 acts to retract the contact members to `their normal central position, as does also the garter spring 8l of the construction shown in Fig. 1. It is obvious that in lieu of seating the garter springr 8 in the external notches of the contact members, such members may be provided with holes or eyes through which a contractile band or other retaining member may be passed, and on which the contact members maybe strung, like a string of beads. Such construction is obvious and well known in this art, and it need not be illustrated.

From the above description it will be apparent that there is thus provided a device of thecharacter described .possessing the particular features of advantage before enumerated as desirable, but which obvigusly is susceptible 'of modification in its form, prov the invention hasbeen described in language i more or less'speciic as to structural features, it is to be understood thatthe invention isl not limited to the specific details shown, but that the means and construction herein disclosed, comprises the preferred formv of several modes of putting the invention into effect and the invention is,therefore, claimed in any of its forms or modifications within the legitimate and valid scope of the appended claims.

Having thus described my invention, 'l claim:

1. In a short circuiting device for coma mutators, a commutator having a concentric recess in its lateral face, an annular series of centrifugally actuated contact members of substantially L-shape arranged in juxta-v position -to thelateral face of the commutator with one arm of such members projecting lwithin the recess and the other arm radially disposed in `normally spaced relation with theflateral face of the commutator, and `an, annular contractile band exteriorly surrounding the series of contact members against fthe tension' of .which said members are'radially movable under centrifugal iniuence vuntil vlimited in such radial movement by the engagement of the lateral arms y annular series of contact members .against the tension of which the contact members are radially movable under centrifugal influence, and a fulcrum engagement effected by the contact members as they approach the limit of their outward radial movement about which the Contact members turn into engagement.\vith the commutator bars under the further centrifugal influence. ,f

3. In a short circulting device for commutators,..an annular series of contact meml bers'v located in juxtaposition to the lateral face of the commutator, and capable of both radial and oscillatory movement under centrifugal iniiuence, said contact members each having an arm projecting laterally therefrom, a fulcrum bearing for said arm, and a yielding tension member common to all the contact members against the yielding resistance of which contact members are capable of initial movement in a radial direction independent of said fulcrum bearing, and subsequently movable about said fulcruin bearing to effect contact with the commutator bars. V

4. In a short circuiting ldevice for commutators, an annular series of contact members located in juxtaposition to thel lateral face of the commutator, and capable of both radial and oscillatory movement under centri-fugal iniiuence, said 4contact members each having an arm projecting laterally therefrom, a fulcrum bearing for said arm,

. in relation with which thecontact member and arm are movable radially into and out of -engagement, said contact members being oscillated irito and 'out of engagement with the commutatorybars about the points of engagement of their arms with the bearing, and a yielding retracting member resisting the movement of the contact members about their fulcrum bearing against the yielding resistance of which the contact members are movable under centrifugal influence.

5. In a 'short circuitlng device for commutators, an annular series of contact members located in juxtaposition to the lateral face of the commutator, and capable of both radial and oscillatory movement under centrifugal influence, said contact members each having alateral projection, a bearing surface with which said projection engages to effect oscillatory movement'of the contact members and a yielding retracting member common to the contact members and having circumferential engagement therewith against the yielding resistance of Which the contact members are movable under centrifugal influence.

6. In a short circuiting device for commutators, an annular series of ccntrifugally controlled contact members capable of radial and tilting movement, stop means enga ed by said contact members during their ra ial movement under centrifugal influence, the engagement of the Contact members with the stop means being in a plane offset in relation with their centers of mass, whereby the continued centrifugal influence will tilt said contact members into engagement with the commutator bars and a yielding retracting member against the yielding resistance of which the contact members effect their tilting movement under centrifugal influence. p

7. In a short circuiter for commutators, an annular series of Contact members initially movable in a radial direction and subsequently tilted into engagement with the commutator bars under centrifugal influence, stop means engaged by the contact members at the limit of their radial movement upon which saidn` contact members will fulcrum for their subsequent tilting movement, and yielding retracting means common to all the contact members initially resisting their radial movement and subsequently resisting their tilting movement at the completion of their original movement.

8. In a short circuiter for electric motors, an annular series .of centrifugally actuated Weights arranged circumferentially and operable radially relative to the motor shaft, and a spring tension member against the resistance of which the weights are initially moved radially, and a fulcrum bearing about .which the weights are subject to oscillatory movement against spring tension at the limit of vtheir radial movement.

9. In a short circuiter for electric motors, an annular series of centrifugally actuated Weights arranged circumferentially and radially movable'relative to the motor shaft, an annular spring band circumferentially surrounding the weights against the yielding resistance of which the radial movement of the Weights is effected, and a stop for said Weights located in a parallel plane'ol'set in relation with that of the band, said weights being capable of subsequent tilting move. ment under centrifugal influence against the yielding resistance of the spring band after the Weights have been arrested in their radial movement by engagement with. said stop.

. 10. In a short circuiter for electric motors, an annular series of centrifugally actuated weights arranged circumferentially of the motor shaft and capable of both radial and tilting movements to effect short circuiting of the motor armature, and a spring member yieldingly resisting the tilting movement of .s 1,640,900 v y E the Weights t0 prevent such tilting movement in advance ofthe other, and an annular conuntil the limit of radial'movement of the tractile'band common to all the Weights of Weights has been reached. the series yieldingly resisting' both the oscilll. ln a short circuiting device for comlatory and the radial movements of said 5 mutators, an annular series o contact mem- Weights. l5A

bers located in juxtaposition to the lateral In testimony whereof, I have hereunto set face of the commutator and capable of both my hand this 28thv day of January, A. l). y oscillatory and radial movements under 1924.

centrifugal inlluence, control means therefor, l0 by which said movements are initiated'one s EVERETT P. LARSH. 

